1. Field of the Invention
This invention generally relates to electric floor cleaners, and more particularly to an electric floor cleaner of the type having a three-phase a.c. motor driven by three-phase a.c. obtained by converting single phase a.c. from a single phase power source.
2. Description of the Prior Art
In conventional electric floor cleaners or polishers, there is a relationship between a brush-driving motor and power source voltage in theory as follows:
(a) A system in which a two-phase 100 volt driving motor is connected to an output side of an inverter whose input is 100 volt and output is 100 volt. This system is referred to as system A. In this specification, the words "inverter system" are used to mean a system which converts an a.c. input into a d.c. by way of a rectifier, and then the d.c. is converted into a desired a.c., and an inverter which simply converts a.c. to d.c. is referred to as "inverter".
(b) A system in which a three-phase 100 volt driving motor is connected to an output side of an inverter whose input is 100 volt and output is 100 volt. This system is referred to as system B.
(c) A system in which a single-phase 100 volt driving motor is operated through primary voltage control. This system is referred to as system C.
(d) A system in which a single-phase 100 volt driving motor is driven directly by commercial power source This system is referred to as system D.
(e) A system in which a d.c. driving motor is operated where commercial power is converted into d.c. by utilizing thyristors or the like. This system is referred to as system E.
(f) A system in which a three-phase 200 volt driving motor is connected to an output side of an inverter whose input is 200 volt and output is 200 volt where the inverter is connected to an output side of a transformer whose input is 100 volt and output is 200 volt. This system is referred to as system F.
The above mentioned conventional systems A to F have the following advantages and disadvantages.